Converting from Conventional to Combi

[debbiea]

Two question:

We have a conventional system with tanks in the loft. The bathroom toilet flushes with water from the cold water tank in loft. What would happen if we convert to a sealed system? How would water get in the toilet?

We currently get a lot of air in our radiators daily which I think is to do with the set up in the loft and sludge. Hoping no underground leak. If there was an underground leak I know a combi would lose pressure overnight. Would a conventional boiler loose pressure too? We never have a problem with our boiler.

 

[Jurassicspark]

Two question:

We have a conventional system with tanks in the loft. The bathroom toilet flushes with water from the cold water tank in loft. What would happen if we convert to a sealed system? How would water get in the toilet?

The pipework feeding the toilet will be changed and it will be connected to the mains water. This will be easy as there will be a sink or a bath nearby so it can be easily tee'd off.

We currently get a lot of air in our radiators daily which I think is to do with the set up in the loft and sludge.

A lack of inhibitor can cause this. Not a problem as it can be topped up during the conversion.

Hoping no underground leak. If there was an underground leak I know a combi would lose pressure overnight. Would a conventional boiler loose pressure too?

It would lose pressure but it will immediately top up by itself through the F and E tank which you won't notice. A combi system will require topping up water as the heating circuit is isolated.

You should be thinking about the requirements needed for the new boiler. How many showers are in the house?

Its not much more expensive to use a hot water cylinder and you can get a higher HW flow rate.

Why do you want to change your system? If everything is working then there isn't a real reason for you to change until something breaks down.

 

[Harry Bloomfield]

We have a conventional system with tanks in the loft. The bathroom toilet flushes with water from the cold water tank in loft. What would happen if we convert to a sealed system? How would water get in the toilet?

It would have to be refed, from the cold water mains, there will already be one, feeding your loft tanks at the moment.

We currently get a lot of air in our radiators daily which I think is to do with the set up in the loft and sludge. Hoping no underground leak. If there was an underground leak I know a combi would lose pressure overnight. Would a conventional boiler loose pressure too? We never have a problem with our boiler.

No point fitting a new boiler, especially a combi, if there is sludge in the system and it is leaking - those problems need addressing first. Pressure in a combi system, is usually higher than an open vented system, so any leaks will be even worse.

 

[debbiea]

There are 2 showers but i’m happy for one to be electric. I’ve been bleeding radiators every week for a long time which seems to be something to do with the tanks in the loft as when there is a lot of air it leaks outside. Following advice on here I have put magnets against some pipes and they stick meaning sludge and water coming out of rads in black. I know I need a powerflush - though house is red hot - but if I got a combi it would do away with the troublesome tanks and pipes in airing cupboard. I’ve had 4 different companies out who can’t be bothered to get to the root of the problem. Lastnone just bent the ballcock which didn’t work and in fact made the air build up worse. Driving me nuts.

 

[debbiea]

Or do I need a leak detective?

 

[Stuckinarut]

If it leaks outside, it suggests the overflow is going, which is either a float valve problem, backfeed (unlikely) or pumping over. If you have sludge/magnetite, then you need a chemical or power flush ASAP, otherwise it might lead to a re-pipe.

Changing to a combi as suggested might not suit you or your setup and I wouldn’t risk damaging a new boiler with an already problematic system. Regards the changeover, it’s known as a conversion, where existing setup is converted to a mains/combi system.

Regular topping up can be a hydrogen buildup from a poorly maintained system and or a leak. Frequently bleeding the air will dilute any inhibitor that may have been present in your system, and is being replaced by oxygenated water, which can further damage/corrode the system.

 

[Notch7]

There are 2 showers but i’m happy for one to be electric. I’ve been bleeding radiators every week for a long time which seems to be something to do with the tanks in the loft as when there is a lot of air it leaks outside. Following advice on here I have put magnets against some pipes and they stick meaning sludge and water coming out of rads in black. I know I need a powerflush - though house is red hot - but if I got a combi it would do away with the troublesome tanks and pipes in airing cupboard. I’ve had 4 different companies out who can’t be bothered to get to the root of the problem. Lastnone just bent the ballcock which didn’t work and in fact made the air build up worse. Driving me nuts.

I was in your situation, constantly bleeding radiators…..but my old boiler started leaking from the heat exchanger so the decision was made for me.

I had actually replaced all the radiators so when the plumber put in a new pressurised system boiler we had a virtually new system apart from the pipework.

I have been super happy with the new system, we got an Ideal boiler which can have 2 temps one for hot water and one for central heating - the heating flow temp is set by a weather comp. It creates a lovely heat as the radiator temp is determined by outside temps, so like today when it’s been 7 deg outside, the flow temp has been 42 deg. It means a nice comfortable temp everywhere. (You need a hot water priority set up, and ideally ultra fast recovery hot water cylinder)

I much prefer it over a combi.

 

[debbiea]

so did you keep the tanks in the loft if it isn’t a combi?

 

[clayton]

You never have a problem with your boiler and the home gets hot, your issue is lack of system maintenance.

 

[debbiea]

Serviced every year. Clearly they aren’t doing their job properly

 

[debbiea]

You never have a problem with your boiler and the home gets hot, your issue is lack of system maintenance.

Serviced every year. Clearly they haven’t been doing their job properly

 

[Notch7]

so did you keep the tanks in the loft if it isn’t a combi?

got rid of expansion tank, kept cold water tank

we have a vented hot water cylinder, I guess an unvented HWC wouldnt require a cold water tank

 

[Notch7]

Serviced every year. Clearly they aren’t doing their job properly

the annual service is only the boiler not the system

old systems get sludge build up and once you get air in the system is accelerates corrosion

Really you need to sort out the system issues -radiators and pipework, whether you have a system boiler or a combi

Do you know what sort of pipework you have -is it conventional 22mm ring with 15mm going to radiators, or is it microbore?

 

[Elsa TLC]

so did you keep the tanks in the loft if it isn’t a combi?

If you have the room, go for a system boiler and an unvented cylinder.

You will then have no tanks in loft and less if any pipework above chest height

 

[Harry Bloomfield]

Serviced every year. Clearly they aren’t doing their job properly

A boiler service, is not a heating system service. You can in fact, DIY the latter.